Luminous jellies and mysterious squid that inhabit a world of almost no light or oxygen; undersea volcanoes, hydrothermal vents, and earthquake faults; layers of natural gas frozen into an ice-like solid in the seafloor. All these can be found in the depths of the Gulf of California, the 1,100-kilometer-long (700-mile-long) finger of water between the peninsula of Baja California and mainland Mexico. Following up on tantalizing discoveries made during a 2003 trip to the gulf, MBARI researchers will be returning to the little-explored region in February 2012 for a three-month expedition. Web visitors can read the researchers’ updates and follow their progress on the expedition homepage.

The 2012 Gulf of California expedition will involve two MBARI research vessels, more than 25 ROV pilots and ships’ crew, and about 60 researchers. The main research vessel will be the Western Flyer, which serves as a host ship for the remotely operated vehicle (ROV) Doc Ricketts. Scientists and pilots guide ROV Doc Ricketts from a control room on board the Western Flyer, and will use this robotic submarine to observe animals, perform experiments, and explore the depths of the gulf.

Serving as a “scout” for the Western Flyer is a second MBARI research vessel, the Zephyr. For this expedition, Zephyr will carry an autonomous underwater vehicle (AUV) that uses sound to create detailed maps of the seafloor. These maps will help the ROV pilots find their way around the ocean bottom and will give scientists some ideas of particularly interesting places to investigate.

Home base for the expedition will be the town of La Paz, near the southern end of the gulf. However, the expedition teams will travel to research sites scattered up and down the gulf, as well as along the Pacific coasts of California and Baja California (see map below). Many of the expedition’s research sites are located in and around the gulf’s deep basins, where active earthquake faults and undersea volcanic activity are common.

To accommodate all the different MBARI scientists who are interested in studying this unique region, the expedition will be divided up into several “legs,” each with a different focus. Most legs of this scientific relay will last about ten days.

Scientists will begin their studies soon after leaving Moss Landing, using the trip down to the gulf as an opportunity to conduct research. During this first leg of the cruise, a team under the direction of biological oceanographer Francisco Chavez will collect a series of water samples from the surface down to depths of 1,000 meters (3,280 feet). Their goal is to chart the course and study the chemistry of a hidden river of water sometimes known as the “California Undercurrent.”

As its name implies, the California Undercurrent flows hundreds of meters beneath the ocean surface. It originates in the tropical Pacific, just south of the Gulf of California, and continues northward at least as far as Monterey Bay. Chavez’ group will look for changes in the water chemistry and in the animals and microscopic algae that are carried along with the California Undercurrent as it travels over 1,000 kilometers (620 miles) northward from Baja California to Central California. This will help scientists understand an important, but little-studied contributor to ocean productivity along the entire California coast.

The second leg of the expedition will focus on animals that live in the open waters of the gulf. Marine biologists led by Steve Haddock will use scuba gear and ROV Doc Ricketts to look at jellies, small fish, and other midwater animals in the central and southern parts of the gulf. The scientists are particularly interested in finding out how these animals have adapted to life at depths where the seawater contains almost no oxygen.

Oxygen minimum layers occur in many parts of the world’s oceans. They are caused by hoards of marine bacteria, which consume oxygen as they decompose bits of marine algae and debris that drift down from the surface. The oxygen minimum layer in the central and southern Gulf of California is unusually thick, and may extend from depths of 250 to 1,000 meters (820 to 3,280 feet). In contrast, Monterey Bay (another area of high biological productivity) may have similarly low oxygen levels only at depths from about 650 to 850 meters (2,130 to 2,790 feet).

Many marine animals spend the daylight hours at depths of hundreds of meters, and migrate up toward the surface at night to feed. Based on observations made during the 2003 cruise to the gulf, the researchers hypothesize that the gulf’s oxygen minimum layer serves as an underwater barrier, confining some marine animals to deep water and concentrating others near the surface, where they may remain even during the daytime.

A few animals have adapted to life in the oxygen minimum layer. Some, like the Humboldt squid, can migrate through the layer, while others, like the Vampire squid, use it as a shelter from predators. During their time at sea, Haddock and his fellow scientists hope to observe, count, and collect animals from different depths to learn how the oxygen minimum layer affects the distributions of animals at different times of day and night.

Leg 3: Life on the seafloor

The third leg of the expedition will focus on animals that live on the seafloor. Researchers led by Jim Barry will compare seafloor life in the northern and southern parts of the gulf. The bottom waters of the northern Gulf of California are unusually warm and rich in oxygen compared to other parts of the ocean. This allows some animals that would normally be found a few hundred meters below the surface to survive down to depths of 1,000 meters (3,280 feet) or more.

In addition to observing and counting animals using ROV Doc Ricketts, Barry’s team will study animals and bacteria that live within the seafloor sediment. By measuring how much oxygen these seafloor organisms use, the researchers can compare the amount of food they consume at different study sites. The researchers will also compare the metabolism of seafloor animals under normal, high-carbon dioxide, and high oxygen conditions to understand how changes in ocean chemistry affect marine life.

Leg 4: Greenhouse gases in the deep sea

During the fourth leg of the gulf expedition, marine chemists led by Peter Brewer will study the behavior of two gases, methane and carbon dioxide, in the high-pressure and low-temperature environment of the gulf’s deep basins. Immense quantities of carbon dioxide are dissolved within the Earth’s oceans and huge amounts of methane (in an ice-like hydrate form) lie within the seafloor. Both gases play important roles in global warming. Thus, scientists are very interested in the behavior of these gases in the ocean and their movement between the ocean and the atmosphere.

Brewer and his team will use ROV Doc Ricketts to study and map several sites in the gulf where natural gas (which is mostly methane) bubbles out of the seafloor. They will also study the composition of this gas using a unique underwater chemical analyzer known as the laser Raman spectrometer. This device will also be used to analyze the chemical structure of methane hydrates, which form layers of ice-like material in the seafloor.

After traveling to the northern part of the gulf, Brewer’s team will perform experiments to study how carbon dioxide, when dissolved in seawater, makes the ocean more acidic. As the concentration of carbon dioxide in Earth’s atmosphere increases due to burning of oil, gas, and coal, such ocean acidification is becoming a serious problem. Brewer’s experiments in the gulf will help in the design of future experiments to test the effects of ocean acidification on a variety of marine organisms.

Legs 5 and 6: Biogeochemistry of faults, vents, and seeps

Legs 5 and 6 of the gulf expedition will involve a collaboration between marine geologists, chemists, and biologists. Scientists from all three of these fields will work together to study the biogeochemistry of seeps—areas where water flows out of the seafloor. In some places, due to nearby volcanic activity, this water is extremely hot, forming underwater hot springs or hydrothermal vents.

Like the geysers at Yellowstone National Park, the hot water in deep-sea hydrothermal vents carries an abundance of dissolved minerals, many of which are toxic to most marine animals. However, a few deep-sea animals have evolved the ability to use these minerals as food (with the help of specialized bacteria). Other animals feed on the bodies or waste products of the vent specialists, eventually forming a miniature, self-contained ecosystem around each hydrothermal vent.

Because the distribution, reproduction, and survival of vent animals are intimately tied to the geology and chemistry of the hydrothermal vents, it takes an interdisciplinary team of scientists to study such sites. Marine geologist Charlie Paull will lead the team on Leg 5, with the goal of learning how the geology of the gulf affects the distribution of seeps and hydrothermal vents, as well as the animals that colonize them. Fellow chief scientists include hydrothermal vent expert Bob Vrijenhoek and marine chemist Ken Johnson.

Seeps and vents often form where the rocks are fractured or weakened by submarine faults. Paull and his team will use ROV Doc Ricketts (as well as seafloor maps created by the AUV team) to look for sea-bottom features like cracks or slumps that indicate where earthquake faults underlie the seafloor. After identifying promising sites, the team will look for signs of fluid flow to determine how it relates to the nearby faulting. In many cases, the most obvious sign of fluid flow is a mat of bacteria on the seafloor or community of seafloor animals such as tube worms.

Each time the scientists find a seep or vent, they will take samples of sediment and vent fluids for chemical analysis. They will also install instruments at some sites to measure how the chemistry of the fluids or the surrounding seawater changes over time.

Biologists on the team will collect animals from the vents for DNA analysis. By looking at the genetics of animals from different vents, the biologists hope to understand how these animals are able to colonize new vents. The colonization process is critical to the survival of vent animals, since individual vents are often dozens or even hundreds of kilometers apart, and each vent community only lasts as long as the fluids keep flowing (which can be as little as a few years in some cases). The biologists will also study the bacteria that allow vent animals to obtain nutrition from chemicals that would be toxic to most other organisms.

Leg 7: Undersea volcanoes, old and new

Scientists on leg 7 of the gulf cruise will explore several underwater volcanoes and a portion of a volcanic spreading center along the East Pacific Rise, an immense underwater mountain range just south of the gulf entrance. Led by geologist Dave Clague, the scientists on this leg will study both the lavas that make up these volcanic areas and the animals that have colonized them.

The Gulf of California lies at the northern end of an immense underwater mountain range called the East Pacific Rise. Base image modified from 1996 NOAA poster, “Age of the Ocean Floor”

Just south of the Gulf of California, the East Pacific Rise breaks into a series of small spreading centers and transform faults. This illustration shows the approximate locations of a few of these features. Arrows show the relative motions of the crust at a few locations. (Base map from Google Earth. Tectonic features adapted from Alvarez et al., Bathymetry and active geological structures in the Upper Gulf of California, Bol. Soc. Geol. Mex v.61 n.1, 2009)

The Gulf of California lies at the northern end of an immense underwater mountain range called the East Pacific Rise. Base image modified from 1996 NOAA poster, “Age of the Ocean Floor”

Clague’s team will use AUV-generated maps of the seafloor to guide ROV Doc Ricketts in examining individual lava flows. They hope to determine if the central portion of the East Pacific Rise had more frequent and longer-lasting eruptions than the sideways-shifting transform faults that extend outward on either side of the ridge. The scientists will also look for areas where remnant heat has created hydrothermal vents and vent-related animal communities.

In addition, the team will investigate several undersea volcanoes that are no longer active, but still form sizable undersea mountains (seamounts). Marine biologists on the ship will use ROV Doc Ricketts to study animals that live in the water above these seamounts and deep-sea corals and sponges that live on the seamounts themselves. The biologists are particularly interested in finding out how animal communities differ between seamounts with summits at different depths below the surface.

Conclusion

During their last visit to the Gulf of California in 2003, MBARI scientists found new hydrothermal vents and observed many unusual deep-water animals in their native habitat. They made discoveries about the chemistry of the gulf’s waters and about the geology of the seafloor. But as is common in scientific endeavors, their work yielded just as many questions for further study as it did answers.

MBARI’s attempted return to the gulf in 2008 was cancelled after the Western Flyer was damaged while entering the port of La Paz. After years of planning and preparation, the 2012 expedition should produce more exciting finds, and will add to the legacy of scientific exploration in this unique and remote marine environment.

Article by Kim Fulton-Bennett and Erin Loury

For more information on this article, please contact Kim Fulton-Bennett:
(831) 775-1835, kfb@mbari.org

Here’s a short video by Erin Loury that describes the 2012 expedition and shows some of the fascinating features of the Gulf that MBARI researchers observed during their 2003 expedition:

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